The global distribution of oral and maxillofacial surgeons: a mixed-methods study

Despite its role in treating the most dominant non-communicable diseases worldwide, the global workforce of oral and maxillofacial (OM) surgeons is not well-characterized. To address the current deficit in understanding of the global OM surgeon workforce and to elevate oral and maxillofacial surgery (OMS) in the global health discourse, we join other surgical specialties in evaluating global surgical capacity with a descriptive analysis of the distribution of OM surgeons worldwide. A mixed-methods study was implemented using a combination of literature review, in-country contacts, internet searches, and survey data. The survey was distributed globally from January to June 2022. Data regarding OM surgeon workforce estimates were obtained for 104 of 195 United Nations-recognized countries (53.3%). Among countries with available estimates, the median global workforce density was 0.518 OM surgeons per 100,000 population. Twenty-eight countries (26.9%) were reported to have two or fewer OM surgeons. The median OM surgeon workforce density for low-income countries was 0.015 surgeons per 100,000 population, compared to 1.087 surgeons per 100,000 population in high-income countries. low and middle-income countries countries have the least workforce density as well as the least data coverage. More work is needed to better understand the capacity of the global OM surgeon workforce and access to OMS care.

Does point-of-care ultrasonography improve diagnostic accuracy in emergency department patients with undifferentiated hypotension? An international randomized controlled trial from the SHOC-ED investigators

PURPOSE

Point-of-care ultrasonography (POCUS) is an established tool in the management of hypotensive patients in the emergency department (ED). We compared the diagnostic accuracy of a POCUS protocol versus standard assessment without POCUS in patients with undifferentiated hypotension.

METHODS

This was an international, multicenter randomized controlled trial included three EDs in North America and three in South Africa from September 2012 to December 2016. Hypotensive patients were randomized to early POCUS protocol plus standard care (POCUS group) or standard care without POCUS (control group). Initial and secondary diagnoses were recorded at 0 and 60 min. The main outcome was measures of diagnostic accuracy of a POCUS protocol in differentiating between cardiogenic and non-cardiogenic shock. Secondary outcomes were diagnostic performance for shock sub-types, as well as changes in perceived category of shock and overall diagnosis.

RESULTS

Follow-up was completed for 270 of 273 patients. For cardiogenic shock, the POCUS-based diagnostic approach (POCUS) performed similarly to the non-POCUS approach (control) for specificity [95.5% (89.9-98.5) vs.93.8% (87.7-97.5)]; positive likelihood ratio (17.92 vs 14.80); negative likelihood ratio (0.21 vs 0.09) and diagnostic odds ratio (85.6 vs 166.57), with a similar overall diagnostic accuracy between the two approaches [93.7% (88-97.2) vs 93.6% (87.8-97.2)]. Diagnostic performance measures were similar across sub-categories of shock.

CONCLUSION

This is the first randomized controlled trial to compare diagnostic performance of a POCUS protocol to standard care without POCUS in undifferentiated hypotensive ED patients. POCUS performed well diagnostically in undifferentiated hypotensive patients, especially as a rule-in test; however, performance did not differ meaningfully from standard assessment.

An introductory course on social identities and their importance in public health

Background

Social identities - e.g., sex/gender, ethnicity, ability, sexual orientation - and their intersections shape health inequalities in societies. Yet, a systematic, critical integration into public health curricula is lacking, especially in the European region. To address this gap, we developed a curriculum on social identities and their importance in public health in collaboration with ASPHER.

Objectives

The curriculum enables students to identify mechanisms of privilege and oppression related to social identities, and to learn how to determine biases within public health structures (and oneself). Moreover, it equips them with tools and skills to address and change biases in their practices to ultimately reduce health inequities.

Results

We conceptualized the curriculum in an iterative and participatory process in a group of students, young professionals and senior researchers from different countries in Western Europe and North America. The curriculum covers three core elements: 1) the introduction of concepts and terminology on diversity, equity and social identities in relation to health inequalities, 2) the reflection on the role of public health professionals and their responsibility within this system; and 3) spotlights on specific social identities, e.g., sex/gender or social class. In addition, it provides guidance on teaching methods to empower a broad range of public health professionals to engage with the course materials more easily.

Conclusions

The curriculum has the potential to strengthen the capacities of future public health professionals to acknowledge the relevance of social identities and how to respond effectively to contribute to health equity. After piloting and revisions, the course will be made available on an open access platform.

Pharmacokinetics of apixaban in patients with end stage renal disease on hemodialysis and atrial fibrillation: results from the RENAL-AF trial

Background/Introduction

Apixaban use is increasing for stroke prevention in patients with atrial fibrillation (AF) and end stage renal disease (ESRD) on hemodialysis. There is uncertainty as to the optimal dose in this population in part related to the limited available pharmacokinetic (PK) data.

Purpose

We comprehensively evaluated the PK of apixaban collected over 1 month of apixaban dosing in 63 patients with AF and ESRD on hemodialysis.

Methods

Patients with AF and ESRD on hemodialysis were randomized to warfarin versus apixaban within the RENAL-AF trial with 5 mg BID dosing, except for 2.5 mg BID in those age ≥80 years or weight ≤60 kg. The 5 mg BID dose could be reduced to 2.5mg BID for minor bleeding. Day 1 PK data was collected on all patients pre- and post-hemodialysis. Day 3 and 1 month pre- and post-hemodialysis PK samples were collected in 49 patients. The timing of apixaban dosing and hemodialysis relative to PK samples was recorded. Dosing history, hemodialysis, and PK samples were chronologically integrated with patient specific data such as body size, age, race and gender. This dataset was combined with the ARISTOTLE dataset, and the published PK model from ARISTOTLE describing exposures in the AF population was updated to incorporate an additional clearance term for hemodialysis. The model estimated apixaban exposures (AUC) in RENAL-AF were compared to ARISTOLTE AUC values.

Results

There were 285 PK concentrations collected among 63 patients in the RENAL-AF trial. Patients had median age 69 years with 41% women (N=26) and a median weight of 84 kg (49, 157). The median AUCs for patients with ESRD on hemodialysis were 5,452 and 2,990 for patients treated with 5mg BID and 2.5mg BID doses, respectively. The median AUCs for patients treated with 5mg BID from ARISTOTLE increased from 2,802 for patients with class 1 CKD to 5,863 for class 4 CKD, while they increased from 2,392 for class 1 CKD to 2,881 for class 4 CKD in patients treated with 2.5mg BID. The median AUC for patients with ESRD on hemodialysis were within 50% of the exposure of patients from ARISTOTLE for all classes of CKD for the 2.5mg BID dose and for classes 2, 3A, 3B, and 4 CKD for the 5mg BID dose (Figure).

Conclusions

The steady state apixaban exposure data in patients with AF and ESRD on hemodialysis were modestly higher but consistent with the results of non-ESRD patients from ARISTOTLE, using 5 mg BID unless patients had age ≥80 years or weight ≤60 kg. Additional clinical outcomes data on the use of apixaban in patients with AF and ESRD on hemodialysis are needed.

Funding Acknowledgement

Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Investigator sponsored grant from Bristol-Myers Squibb and Pfizer

Barriers and enablers to detection and management of chronic kidney disease in primary healthcare: a systematic review

Background

Chronic kidney disease (CKD) is growing population health concern worldwide, and with early identification and effective management, kidney disease progression can be slowed or prevented. Most patients with risk factors for chronic kidney disease are treated within primary healthcare. Therefore, it is important to understand how best to support primary care providers (PC-P) to detect and manage chronic kidney disease. The aim of this systematic review was to evaluate barriers and enablers to the diagnosis and management of CKD in primary care.

Methods

A systematic review of qualitative research on the barriers and/or enablers to detection and/or management of CKD in adults within primary healthcare was conducted. The databases Medline (EBSCO), PubMed, Cochrane CENTRAL, CINAHL (EBSCO) and Joanna Briggs Institute Evidence Based Practice (Ovid) were searched until 27th August 2019. Barriers and/or enablers reported in each study were identified, classified into themes, and categorised according to the Theoretical Domains Framework.

Results

A total of 20 studies were included in this review. The most commonly reported barriers related to detection and management of CKD in primary care were categorised into the ‘Environmental context and resources’ domain (n = 16 studies). Overall, the most common barrier identified was a lack of time (n = 13 studies), followed by a fear of delivering a diagnosis of CKD, and dissatisfaction with CKD guidelines (both n = 10 studies). Overall, the most common enabler identified was the presence of supportive technology to identify and manage CKD (n = 7 studies), followed by the presence of a collaborative relationship between members of the healthcare team (n = 5 studies).

Conclusion

This systematic review identified a number of barriers and enablers which PC-P face when identifying and managing CKD. The findings of this review suggest a need for time-efficient strategies that promote collaboration between members of the healthcare team, and practice guidelines which consider the frequently co-morbid nature of CKD. Enhanced collaboration between PC-P and nephrology services may also support PC-Ps when diagnosing CKD in primary care, and facilitate improved patient self-management.

Daytime sleepiness and its relationships to fatigue and autonomic dysfunction in adults with spinal cord injury

OBJECTIVE

To determine the extent of daytime sleepiness in adults with spinal cord injury (SCI) and investigate the contribution of fatigue and autonomic function to sleepiness status.

METHODS

Participants included 45 adults with SCI attending outpatient services or living in the community and 44 able-bodied controls. The Oxford Sleep Resistance Test (OSLER) was used to assess daytime sleepiness, while eye blink rate duration (electrooculography) and the Iowa Fatigue Scale assessed fatigue. Heart rate variability (HRV) was used to assess autonomic function. Survival analysis (Kaplan Meier) was used to estimate the rate of loss in participation in the OSLER task, as a measure of daytime sleepiness. Repeated measures ANOVA was used to determine HRV differences between groups. Regression analysis was used to establish factors that contributed to daytime sleepiness.

RESULTS

Participants with high lesions ("T3 and above") had significantly increased daytime sleepiness. OSLER results revealed only 33% of those with high lesions remained awake during the task. Those with high lesions also had significantly reduced sympathetic activity while no differences in parasympathetic activity were found between groups. Lesion completeness had no effect. Standardized variation in heart rate, slow eye blinks, low frequency HRV and self-reported fatigue contributed to daytime sleepiness.

CONCLUSION

Neurological lesions at "T3 or above" have an increased risk of daytime sleepiness, impacting on independence in daily functional tasks and work performance. Autonomic imbalance alters cardiovascular control, affecting health and wellbeing. The interaction of these factors requires further investigation.

KRAS induces lung tumorigenesis through microRNAs modulation

Oncogenic KRAS induces tumor onset and development by modulating gene expression via different molecular mechanisms. MicroRNAs (miRNAs) are small non-coding RNAs that have been established as main players in tumorigenesis. By overexpressing wild type or mutant KRAS (KRASG12D) and using inducible human and mouse cell lines, we analyzed KRAS-regulated microRNAs in non-small-cell lung cancer (NSCLC). We show that miR-30c and miR-21 are significantly upregulated by both KRAS isoforms and induce drug resistance and enhance cell migration/invasion via inhibiting crucial tumor suppressor genes, such as NF1, RASA1, BID, and RASSF8. MiR-30c and miR-21 levels were significantly elevated in tumors from patients that underwent surgical resection of early stages NSCLC compared to normal lung and in plasma from the same patients. Systemic delivery of LNA-anti-miR-21 in combination with cisplatin in vivo completely suppressed the development of lung tumors in a mouse model of lung cancer. Mechanistically, we demonstrated that ELK1 is responsible for miR-30c and miR-21 transcriptional activation by direct binding to the miRNA proximal promoter regions. In summary, our study defines that miR-30c and miR-21 may be valid biomarkers for early NSCLC detection and their silencing could be beneficial for therapeutic applications.

Repression of Esophageal Neoplasia and Inflammatory Signaling by Anti-miR-31 Delivery In Vivo

BACKGROUND

Overexpression of microRNA-31 (miR-31) is implicated in the pathogenesis of esophageal squamous cell carcinoma (ESCC), a deadly disease associated with dietary zinc deficiency. Using a rat model that recapitulates features of human ESCC, the mechanism whereby Zn regulates miR-31 expression to promote ESCC is examined.

METHODS

To inhibit in vivo esophageal miR-31 overexpression in Zn-deficient rats (n = 12-20 per group), locked nucleic acid-modified anti-miR-31 oligonucleotides were administered over five weeks. miR-31 expression was determined by northern blotting, quantitative polymerase chain reaction, and in situ hybridization. Physiological miR-31 targets were identified by microarray analysis and verified by luciferase reporter assay. Cellular proliferation, apoptosis, and expression of inflammation genes were determined by immunoblotting, caspase assays, and immunohistochemistry. The miR-31 promoter in Zn-deficient esophagus was identified by ChIP-seq using an antibody for histone mark H3K4me3. Data were analyzed with t test and analysis of variance. All statistical tests were two-sided.

RESULTS

In vivo, anti-miR-31 reduced miR-31 overexpression (P = .002) and suppressed the esophageal preneoplasia in Zn-deficient rats. At the same time, the miR-31 target Stk40 was derepressed, thereby inhibiting the STK40-NF-κΒ-controlled inflammatory pathway, with resultant decreased cellular proliferation and activated apoptosis (caspase 3/7 activities, fold change = 10.7, P = .005). This same connection between miR-31 overexpression and STK40/NF-κΒ expression was also documented in human ESCC cell lines. In Zn-deficient esophagus, the miR-31 promoter region and NF-κΒ binding site were activated. Zn replenishment restored the regulation of this genomic region and a normal esophageal phenotype.

CONCLUSIONS

The data define the in vivo signaling pathway underlying interaction of Zn deficiency and miR-31 overexpression in esophageal neoplasia and provide a mechanistic rationale for miR-31 as a therapeutic target for ESCC.

MicroRNA-148a reduces tumorigenesis and increases TRAIL-induced apoptosis in NSCLC

Nonsmall cell lung cancer (NSCLC) is one of the leading causes of death worldwide. TNF-related apoptosis-inducing ligand (TRAIL) has been shown to induce apoptosis in malignant cells without inducing significant toxicity in normal cells. However, several carcinomas, including lung cancer, remain resistant to TRAIL. MicroRNAs (miRNAs) are small noncoding RNAs of ∼ 24 nt that block mRNA translation and/or negatively regulate its stability. They are often aberrantly expressed in cancer and have been implicated in increasing susceptibility or resistance to TRAIL-induced apoptosis by inhibiting key functional proteins. Here we show that miR-148a is down-regulated in cells with acquired TRAIL-resistance compared with TRAIL-sensitive cells. Enforced expression of miR-148a sensitized cells to TRAIL and reduced lung tumorigenesis in vitro and in vivo through the down-modulation of matrix metalloproteinase 15 (MMP15) and Rho-associated kinase 1 (ROCK1). These findings suggest that miR-148a acts as a tumor suppressor and might have therapeutic application in the treatment of NSCLC.

A set of NF-κB-regulated microRNAs induces acquired TRAIL resistance in lung cancer

TRAIL (TNF-related apoptosis-inducing ligand) is a promising anticancer agent that can be potentially used as an alternative or complementary therapy because of its specific antitumor activity. However, TRAIL can also stimulate the proliferation of cancer cells through the activation of NF-κB, but the exact mechanism is still poorly understood. In this study, we show that chronic exposure to subtoxic concentrations of TRAIL results in acquired resistance. This resistance is associated with the increase in miR-21, miR-30c, and miR-100 expression, which target tumor-suppressor genes fundamental in the response to TRAIL. Importantly, down-regulation of caspase-8 by miR-21 blocks receptor interacting protein-1 cleavage and induces the activation of NF-κB, which regulates these miRNAs. Thus, TRAIL activates a positive feedback loop that sustains the acquired resistance and causes an aggressive phenotype. Finally, we prove that combinatory treatment of NF-κB inhibitors and TRAIL is able to revert resistance and reduce tumor growth, with important consequences for the clinical practice.

Developing a spinal cord injury research strategy using a structured process of evidence review and stakeholder dialogue. Part II: Background to a research strategy

STUDY DESIGN

Literature review/semi-structured interviews.

OBJECTIVE

To develop a spinal cord injury (SCI) research strategy for Australia and New Zealand.

SETTING

Australia.

METHODS

The National Trauma Research Institute Forum approach of structured evidence review and stakeholder consultation was employed. This involved gathering from published literature and stakeholder consultation the information necessary to properly consider the challenge, and synthesising this into a briefing document.

RESULTS

A research strategy 'roadmap' was developed to define the major steps and key planning questions to consider; next, evidence from published SCI research strategy initiatives was synthesised with information from four one-on-one semi-structured interviews with key SCI research stakeholders to create a research strategy framework, articulating six key themes and associated activities for consideration. These resources, combined with a review of SCI prioritisation literature, were used to generate a list of draft principles for discussion in a structured stakeholder dialogue meeting.

CONCLUSION

The research strategy roadmap and framework informed discussion at a structured stakeholder dialogue meeting of 23 participants representing key SCI research constituencies, results of which are published in a companion paper. These resources could also be of value in other research strategy or planning exercises.

SPONSORSHIP

This project was funded by the Victorian Transport Accident Commission and the Australian and New Zealand Spinal Cord Injury Network.

Novel synthesis and characterization of a collagen-based biopolymer initiated by hydroxyapatite nanoparticles

In this study, we developed a novel synthesis method to create a complex collagen-based biopolymer that promises to possess the necessary material properties for a bone graft substitute. The synthesis was carried out in several steps. In the first step, a ring-opening polymerization reaction initiated by hydroxyapatite nanoparticles was used to polymerize d,l-lactide and glycolide monomers to form poly(lactide-co-glycolide) co-polymer. In the second step, the polymerization product was coupled with succinic anhydride, and subsequently was reacted with N-hydroxysuccinimide in the presence of dicyclohexylcarbodiimide as the cross-linking agent, in order to activate the co-polymer for collagen attachment. In the third and final step, the activated co-polymer was attached to calf skin collagen type I, in hydrochloric acid/phosphate buffer solution and the precipitated co-polymer with attached collagen was isolated. The synthesis was monitored by proton nuclear magnetic resonance, infrared and Raman spectroscopies, and the products after each step were characterized by thermal and mechanical analysis. Calculations of the relative amounts of the various components, coupled with initial dynamic mechanical analysis testing of the resulting biopolymer, afforded a preliminary assessment of the structure of the complex biomaterial formed by this novel polymerization process.

MicroRNAs in lung cancer

MicroRNAs have become recognized as key players in the development of cancer. They are a family of small non-coding RNAs that can negatively regulate the expression of cancer-related genes by sequence-selective targeting of mRNAs, leading to either mRNA degradation or translational repression. Lung cancer is the leading cause of cancer-related death worldwide with a substantially low survival rate. MicroRNAs have been confirmed to play roles in lung cancer development, epithelial-mesenchymal transition and response to therapy. They are also being studied for their future use as diagnostic and prognostic biomarkers and as potential therapeutic targets. In this review we focus on the role of dysregulated microRNA expression in lung tumorigenesis. We also discuss the role of microRNAs in therapeutic resistance and as biomarkers. We further look into the progress made and challenges remaining in using microRNAs for therapy in lung cancer.

MiR-34a/c-Dependent PDGFR-α/β Downregulation Inhibits Tumorigenesis and Enhances TRAIL-Induced Apoptosis in Lung Cancer

Lung cancer is the leading cause of cancer mortality in the world today. Although some advances in lung cancer therapy have been made, patient survival is still poor. MicroRNAs (miRNAs) can act as oncogenes or tumor-suppressor genes in human malignancy. The miR-34 family consists of tumor-suppressive miRNAs, and its reduced expression has been reported in various cancers, including non-small cell lung cancer (NSCLC). In this study, we found that miR-34a and miR-34c target platelet-derived growth factor receptor alpha and beta (PDGFR-α and PDGFR-β), cell surface tyrosine kinase receptors that induce proliferation, migration and invasion in cancer. MiR-34a and miR-34c were downregulated in lung tumors compared to normal tissues. Moreover, we identified an inverse correlation between PDGFR-α/β and miR-34a/c expression in lung tumor samples. Finally, miR-34a/c overexpression or downregulation of PDGFR-α/β by siRNAs, strongly augmented the response to TNF-related apoptosis inducing ligand (TRAIL) while reducing migratory and invasive capacity of NSCLC cells.

Abstract LB-241: Silencing of microRNA-31 prevents esophageal neoplasia in zinc deficient rats

Dietary zinc deficiency (ZD) is implicated in the pathogenesis of human esophageal squamous cell carcinoma (ESCC). microRNA-31 (miR-31) is overexpressed in human ESCC. In the rat a ZD diet promotes esophageal carcinogenesis by inducing cellular proliferation and changes in the expression of microRNA and mRNA, including overexpression of miR-31 and cancer-related proinflammation genes. Here we report that treatment of ZD rats with locked nucleic acid (LNA)-modified inhibitor of miR-31 (LNA-antimiR) prevents the development of a precancerous esophageal phenotype. Weanling rats were fed ZD or zinc-sufficient (ZS) diet for 5 weeks. Simultaneously, ZD rats were administered intravenously (twice a week) LNA-antimiR, LNA-scramble miR-31 or the vehicle saline. ZS rats received saline. Compared to ZS rats, LNA-scramble miR-31-treated or saline-treated ZD rats overexpressed miR-31 and displayed a highly proliferative and inflammatory esophageal phenotype. Treatment of ZD rats with LNA-antimiR reduced miR-31 expression in esophageal epithelia and circulating blood by ~60% and reversed the ZD-induced esophageal pathology, as evidenced by a thinned esophageal epithelium with reduced cell proliferation by PCNA immunohistochemistry and increased apoptosis by caspase-3/7 activity. Transcriptome analyses of esophageal epithelia demonstrated derepression of target mRNAs with miR-31 seed sites. In particular, Stk40 (a negative regulator of NF-κ? signaling) was demonstrated to be a bona fide miR-31 target. Using in situ hybridization and immunohistochemistry, miR-31 overexpression in ZD esophageal sections correlated with downregulation of STK40 protein, as well as with upregulation of an NF-κ? p65 - RAGE-S100A9 inflammatory pathway that in turn, was normalized by miR-31 silencing. Thus, silencing miR-31 prevents esophageal neoplasia. Overexpression of miR-31 promotes ESCC initiation by enhancing inflammation via STK40 - NF-κ? signaling. The data indicate that miR-31 may be a promising therapeutic target for improved ESCC diagnosis and prevention. Funding: National Institutes of Health grants U01 CA152758 to CMC and R01CA118560 & R21CA152505 to LYYF.

Citation Format: Cristian Taccioli, Hongping Chen, Michela Garofalo, Yubao Jiang, Gianpiero Di Leva, Hansjuerg Alder, Justin Middleton, Karl J. Smalley, Arianna Bottoni, Stefan Costinean, John L. Farber, Carlo M. Croce, Louise Y Y Fong. Silencing of microRNA-31 prevents esophageal neoplasia in zinc deficient rats. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-241. doi:10.1158/1538-7445.AM2013-LB-241

Numerical modelling of the fibre-matrix interaction in biaxial loading for hyperelastic soft tissue models

This paper assumes that a neo-Hookean matrix with neo-Hookean fibres is representative of soft tissue. Under this assumption, a unit cell model is proposed to investigate the fibre-matrix interfacial stress field for biological soft tissue under biaxial loadings. In this unit cell model, the soft tissue is treated as a composite where the matrix is unidirectionally reinforced with a single family of aligned fibres. The results are compared with the model of Guo et al., which accounts for the fibre-matrix interfacial stress field, and Qiu and Pence's model, which does not proceed from the assumption that the fibres are themselves neo-Hookean. It is found that the stress representative of the fibre-matrix interface plays an important role in the deformation of the composite, and the model of Guo et al. underestimates this stress under large biaxial deformation.

Parametric study of a Hill-type hyperelastic skeletal muscle model

Hill's one-dimensional three-element model has often been used for formulating a three-dimensional skeletal muscle constitutive model, which generally involves several material parameters. However, only few of these parameters have physical meanings and can be experimentally determined. In this paper, a parametric study of a Hill-type hyperelastic skeletal muscle model is performed. First, the Hill-type hyperelastic skeletal muscle model is formulated, containing 13 material parameters. The values or value ranges of these parameters are discussed. The muscle model is then used to predict the behaviour of New Zealand white rabbit hind leg muscle tibialis anterior and a sensitivity study of several parameters is performed. Results show that some parameters in the muscle model can be experimentally determined, some parameters have their own value ranges and the muscle model can predict the experimental data by tuning the parameters within their value ranges. The results from the sensitivity study can help understand how some parameters influence the total muscle stress.

Modelling skeletal muscle fibre orientation arrangement

Skeletal muscle tissues have complex geometries. In addition, the complex fibre orientation arrangement makes it quite difficult to create an accurate finite element muscle model. There are many possible ways to specify the complex fibre orientations in a finite element model, for example defining a local element coordinate system. In this paper, an alternative method using ABAQUS, which is combination of the finite element method and the non-uniform rational B-spline solid representation, is proposed to calculate the initial fibre orientations. The initial direction of each muscle fibre is specified as the tangent direction of the NURBS curve which the fibre lies on, and the directions of the deformed fibres are calculated from the initial fibre directions, the deformation gradients and the fibre stretch ratios. Several examples are presented to demonstrate the ability of the proposed method. Results show that the proposed method is able to characterise both the muscle complex fibre orientation arrangement and its complex mechanical response.

A visco-hyperelastic model for skeletal muscle tissue under high strain rates

In this paper, a visco-hyperelastic skeletal muscle model is developed. The constitutive relation is based on the definition of a Helmholtz free energy function. It is assumed that the Helmholtz energy can be decomposed into volumetric and isochoric parts; furthermore, the isochoric energy can be decoupled into hyperelastic and viscous parts. The model developed involves 14 material parameters and its performance is evaluated by comparing the finite element simulation results with the published experimental studies on the New Zealand white rabbit tibialis anterior muscle. Results show that this model is able to describe the visco-hyperelastic behaviour of both passive and active skeletal muscle tissues under high strain rates (10/s and 25/s).

RANK, RANKL and osteoprotegerin in bone biology and disease

Upon the discovery of RANK, RANKL and OPG in the late 1990s, their importance in the maintenance of the skeletal structure and their dramatic role in bone disease were largely unexpected. In recent years the understanding of these proteins, in particular their regulation, has greatly increased. This review aims to bring the interested reader up to date with the latest news and views on the mechanisms controlling bone resorption in normal and pathological conditions.

Differential expression of syndecans and glypicans in chronically inflamed synovium

BACKGROUND

Membrane-bound heparan sulphate proteoglycans (HSPGs) act as co-receptors and presenters of cytokines and are involved in cell-matrix and cell-cell adhesion.

AIM

To investigate which HSPGs are expressed in knee joint synovia from patients with different forms of arthritis and normal individuals.

METHODS

Synovial samples were obtained from patients with early rheumatoid arthritis (n = 8), longstanding rheumatoid arthritis (n = 13), psoriatic arthritis (n = 7), osteoarthritis (n = 6) and normal joints (n = 12). Expression of syndecan-1, -2, -3 and -4 and glypican-1, -3 and -4 was analysed by immunohistochemistry and dual label immunofluorescence.

RESULTS

The expression of HSPGs in chronically inflamed synovium exhibited a differential distribution. Syndecan-1 was present in the mononuclear infiltrates of synovia from patients with rheumatoid and psoriatic arthritis where it was expressed by plasma cells. Syndecan-2 was present mainly in blood vessels where it occurred on endothelial cells, pericytes and smooth muscle cells. Syndecan-3 stained intensely in endothelial cells but also occurred in sublining macrophages and the lining layer. Glypican-4 occurred in the lining layer and blood vessels. Increased expression of these HSPGs was apparent in rheumatoid and psoriatic compared to osteoarthritic and normal synovia. Little or no staining for syndecan-4, glypican-1 and glypican-3 was seen in all samples.

DISCUSSION

Selected HSPGs, such as syndecan-1, -2 and -3 and glypican-4, could play a part in the pathophysiology of arthritis, such as the migration and retention of leukocytes and angiogenesis in the chronically inflamed synovium.

Electroencephalographic slowing and reduced reactivity in neuropathic pain following spinal cord injury

STUDY DESIGN

Brain wave activity in people with paraplegia, with and without neuropathic pain, was compared to brain wave activity in matched able-bodied controls.

OBJECTIVES

To investigate whether spinal cord injury with neuropathic pain is associated with a slowing of brain wave activity.

SETTING

Australia.

METHODS

Electroencephalographic (EEG) data were collected in the eyes open (EO) and eyes closed (EC) states from 16 participants with paraplegia (eight with neuropathic pain and eight without pain) and matched able-bodied controls. Common EEG artefacts were removed using independent component analysis (ICA). Peak frequency in the theta-alpha band and EEG power in the delta, theta, alpha and beta frequency bands were compared between groups.

RESULTS

The results show significant slowing of the EEG in people with neuropathic pain, consistent with the presence of thalamocortical dysrhythmia (TCD). Furthermore, people with neuropathic spinal cord injury (SCI) pain had significantly reduced EEG spectral reactivity in response to increased or decreased sensory input flowing into the thalamocortical network, as modulated by the eyes open and eyes closed states.

CONCLUSION

The results provide further evidence for alterations in brain electric activity that may underlie the development of neuropathic pain following SCI.

Matrix metalloproteinase 10 promotion of collagenolysis via procollagenase activation: implications for cartilage degradation in arthritis

OBJECTIVE

We have previously reported the up-regulation of matrix metalloproteinase 10 (MMP-10) following treatment with the procatabolic stimulus of interleukin-1 (IL-1) and oncostatin M (OSM) in chondrocytes. Although MMP-10 is closely related to MMP-3, little is known about the role of MMP-10 in cartilage catabolism. The purpose of this study was to determine whether MMP-10 is expressed in connective tissue cells and to assess how it may contribute to cartilage collagenolysis.

METHODS

MMP gene expression was assessed by real-time polymerase chain reaction using RNA from human articular chondrocytes and synovial fibroblasts stimulated with IL-1 plus OSM or tumor necrosis factor alpha (TNFalpha) plus OSM. Synovial fluid levels of MMP-10 were determined by specific immunoassay. Recombinant procollagenases were used in activation studies. Immunohistochemistry assessed MMP-10 expression in diseased joint tissues.

RESULTS

MMP-10 expression was confirmed in both chondrocytes and synovial fibroblasts following stimulation with either IL-1 plus OSM or TNFalpha plus OSM, and MMP-10 was detected in synovial fluid samples from patients with various arthropathies. Exogenous MMP-10 significantly enhanced collagenolysis from IL-1 plus OSM-stimulated cartilage, and MMP-10 activated proMMP-1, proMMP-8, and proMMP-13. Immunohistochemistry revealed the presence of MMP-10 in the synovium and cartilage of an IL-1 plus OSM-induced model of arthritis as well as in samples of diseased human tissues.

CONCLUSION

We confirm that both synovial fibroblasts and articular chondrocytes express MMP-10 following treatment with procatabolic stimuli. Furthermore, the detectable levels of synovial fluid MMP-10 and the histologic detection of this proteinase in diseased joint tissues strongly implicate MMP-10 in the cartilage degradome during arthritis. The ability of MMP-10 to superactivate procollagenases that are relevant to cartilage degradation suggests that this activation represents an important mechanism by which this MMP contributes to tissue destruction in arthritis.

Three-dimensional finite element modelling of the human ACL: simulation of passive knee flexion with a stressed and stress-free ACL

In this study, a three-dimensional finite element model of the human anterior cruciate ligament (ACL) was developed and simulations of passive knee flexion were performed. The geometrical model of the ACL was built from experimental measurements performed on a cadaveric knee specimen which was also subjected to kinematics tests. These experiments were used to enforce the particular boundary conditions used in the numerical model. A previously developed transversely isotropic hyperelastic material model was implemented and the ability to pre-stress the ligament was also included. The model exhibited the key characteristics of connective soft tissues: anisotropy, nonlinear behaviour, large strains, very high compliance for compressive or bending loading along the collagen fibres and incompressibility. Simulations of passive knee flexion were performed, with and without pre-stressing the ACL. The resultant force generated by the ACL was monitored and the results compared to existing experimental data. The stress distribution within the ligament was also assessed. When the ACL was pre-stressed, there was a good correlation between the predicted and experimental resultant forces reported in the literature over the entire flexion-extension range. The stress distribution in the pre-stressed and stress-free ACL were similar, although the magnitudes in the pre-stressed ACL were higher, particularly at low flexion angles.